(A) Field of the Invention
The present invention relates to a standard source, and more particularly, to a standard radiation source.
(B) Description of the Related Art
All objects with temperature above absolute zero emit radiation, which can be measured by non-contact techniques for evaluating the temperature of the objects. Due to the rapid improvement of non-contact techniques, there are a variety of temperature-measuring devices such as the infrared thermal image apparatus or the radiation thermometer available for providing a safe and convenient temperature measurement. Nowadays, the calibration of the non-contact infra-red ear thermometer generally uses a cavity-shaped black body as the standard radiation source for temperature calibration at several degrees, as required by international standards such as ASTM 1965-98, EN 12470-5:2003, and JIS T 4207:2005. Therefore, how to prepare a radiation black body with high temperature uniformity and high resistance to environmental temperature variations has become a very important issue for non-contact temperature measurement techniques.
To perform temperature calibration at several degrees using a cavity-shaped black body as the standard radiation source, the ear thermometer detects the radiation temperature of the cavity-shaped black body directly. However, the cavity-shaped black body generally uses an open cavity design without isolation from the environment, and the radiation temperature of the cavity-shaped black body is likely to be influenced by the repeated thermal exchange between the cavity and the environment at very high or very low temperature if the temperature variation of the environment is very dramatic. Consequently, the temperature uniformity of the cavity-shaped black body is very poor, which will result in imprecise temperature calibrations for the ear thermometer.